Polymerization inhibitors are currently used for partially or fully inhibiting polymerization that may occur during storage or under certain process conditions. In practice, inhibiting a polymerization can become difficult because polymerization will almost always occur even when inhibitors are present, and especially if a polymerization initiator is also present.
The initiation of polymerization can be delayed by encapsulating the polymerization initiator with capsule of organic polymer. Encapsulation delays the initiation of the polymerization until the capsule of organic polymer dissolves or is otherwise compromised to release the initiator into the system containing the monomer.
Encapsulated initiators for polymerization reactions in wellbores have been described in U.S. Pat. No. 7,441,599 to Hermes et al. entitled “Controlling the Pressure within an Annular Volume of a Wellbore,” incorporated by reference herein. The capsules manage the problem of annular build-up of trapped pressure, and would work for applications where polymerization, or activity of inorganic materials, could be delayed for relatively short periods (hours or days) of time. Once the capsule dissolves or is mechanically compromised, the active ingredients are released.
Sometimes a much longer delay than just a few hours or days may be needed. A delay longer than a few weeks may be needed. For various oil well related applications, such as those described in Hermes et al., a delay of months or even years may be needed. For example, Hermes et al. may require a delay of months or even years from the time of emplacement of a reactive spacer fluid that includes a polymerizable monomer to the time of completion of the well and/or production schedule. Capsules of soluble polymer are unsuitable for achieving such a long delay.
Suitable encapsulated compositions that can provide longer delays for initiating polymerization reactions, and other types of chemical reactions, are desirable.